Thiolation of trimethylantimony: Identification and structural characterization

Antimony (Sb), a re-emerging contaminant, has received increasing attentions. The toxicity and mobility of Sb depend on its species. However, little knowledge was available about its multiple chemical species in the environment. Here, we identified and characterized a previously unknown Sb species, trimethylmonothioantimony (TMMTSb). TMMTSb was readily formed when trimethylantimony (TMSb) reacted with sulfide. TMMTSb was separated using HPLC-ICP-MS and further identified by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), and the results show the existence of [SbSC₃H₁₀]⁺, [SbSC₃H₉Na]⁺, and [SbSC₃H₉K]⁺. The formation of Sb-S bond in TMMTSb was evidenced by the Raman shift at 419 cm^-1 compared with that in TMSb. Conclusively, the molecular formula was verified as SbS(CH₃)₃. Sb L_III-edge X-ray absorption near edge structure (XANES) spectrum revealed a higher intensity of the pre-edge peak at 4137 eV of TMMTSb than that of TMSb. The formation of TMMTSb was observed when the microbiota enriched from hot spring sediments and paddy soil were incubated with TMSb. Sulfate-reducing bacteria may be involved in the formation of TMMTSb. The finding of this thiolated methylantimony species may pave a new avenue for exploring the fate of Sb in the environment.